Lethal Effects of Imergard WP, a Perlite-based Dust, on Amblyomma americanum (Ixodida: Ixodidae) Larvae and Nymphs

As resistance in economically and medically important ixodids (hard ticks, Ixodida: Ixodidae) to conventional synthetic toxin-based acaricides has become increasingly widespread, research efforts to identify alternative control tactics have intensified. Laboratory bioassays on the lone star tick, Amblyomma americanum (L.), as a model for other ixodid species, were conducted to assess the efficiency of Imergard WP perlite-based dust versus CimeXa, a silica gel-based insecticidal product that is highly effective against ixodid larvae and nymphs. Each of the two inert desiccant dusts immobilized A. americanum larvae and nymphs within 4-6 h, and killed 100% of the ixodids by 24 h after contact by brief immersion in dry dusts, and after they crawled ≈7.3 cm across a filter paper disc treated with the dusts. Contact by crawling on a dried aqueous film of the dusts, however, did not immobilize and kill the ixodids by 24 h. Similar to silica gel-based desiccant dust, dry perlite-based Imergard WP dust might prophylactically protect cattle and other animals from medically and agriculturally important ixodid pests. Perlite can potentially be stored indefinitely, it can retain its lethal properties for as long as adequate amounts remain on a substrate, and it might be acceptable for limited application in environmentally sensitive habitats.

Desiccant Dusts, With and Without Bioactive Botanicals, Lethal to Rhipicephalus (Boophilus) microplus Canestrini (Ixodida: Ixodidae) in the Laboratory and on Cattle

The exotic southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae), since its eradication from the United States in 1943, made a strong incursion into Texas, beginning 2016. The pest is arguably the most economically detrimental ectoparasite of cattle, Bos taurus L., worldwide. Current R. (B.) microplus control mostly relies on conventional synthetic acaricides to which the ixodid has been developing resistance. Our study demonstrates that commercially available desiccant dust products, with and without bioactive botanical additives, are strongly lethal, when applied dry, against larval R. (B.) microplus in the laboratory, and after being released on dust-treated cattle. Deadzone (renamed Celite 610, a diatomaceous earth product), Drione (silica gel + pyrethrins + piperonyl butoxide synergist), and EcoVia (silica gel + thyme oil), each prophylactically prevented larval R. (B.) microplus from attaching to and feeding on stanchioned calves. Desiccant dust-based products are less likely than conventional synthetic acaricides to decline in terms of efficacy as a result of ixodid resistance, and other desiccant dust advantages, including extended residual, flexibility in terms of application methods, environmental, animal, and human safety, and possible compatibility with organic, or 'green', production systems, are discussed. We anticipate that the desiccant dusts we evaluated, and others not included in this study (e.g., kaolin, perlite, and silica gel) will be effective when used with other control tactics in integrated pest management approaches for controlling R. (B.) microplus (and other ixodid species).

Lethal Effects of Commercial Kaolin Dust and Silica Aerogel Dust With and Without Botanical Compounds on Horn Fly Eggs, Larvae, Pupae, and Adults in the Laboratory

The horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae), is an important bloodsucking ectoparasite of cattle throughout much of the world. The fly is mostly controlled using conventional synthetic insecticides but as concerns about resistance increase, alternative tactics have come under heightened scrutiny. Four desiccant dust products: Surround WP, a kaolin clay-based wettable powder; CimeXa, comprised of silica aerogel; Drione, silica aerogel + pyrethrins; and EcoVia, silica aerogel + thyme oil, were assessed for their lethal effects against horn fly eggs, larvae, pupae, and adults, under laboratory conditions. Although Surround WP and CimeXa did not prevent egg hatching and (when mixed with manure substrate) pupal development, the two products were associated with moderate reductions of emerged adults, and with complete adult contact mortality within 6 hr and 24 hr, respectively. Drione and EcoVia eliminated egg hatching, pupal development, and adults within 15 min to 1 hr, respectively, whether the flies were exposed to treated filter paper substrate or exposed by immersion in the dusts. Implications for horn fly control and advantages of inert desiccant dust formulations are discussed.

Repellency of p-Anisaldehyde Against Musca domestica (Diptera: Muscidae) in the Laboratory

The house fly, Musca domestica L. (Diptera: Muscidae), is a nuisance pest often associated with livestock production, and it can also mechanically transmit the causal agents of human and veterinary diseases. We found that a 0.5% concentration of p-anisaldehyde, produced by many plants consumed by humans, repelled adult M. domestica in static air olfactometer tubes under laboratory conditions for ≥24 h, but by 48 h the repellent activity had worn off. Repellency, however, was not observed in response to 0.5% p-anisaldehyde that had been exposed to sunlight radiation lamps for 2 h. When p-anisaldehyde was aged in darkness for 48 h, it showed strong initial repellency for <1 h. The repellent action of 0.5% p-anisaldehyde was sufficient to keep adult M. domestica from landing on three different food sources when the botanical substance was misted onto the food sources, and when it was placed in proximity to, but not in contact with, the food sources. Extension of p-anisaldehyde's repellent action using solvents other than acetone is discussed.

Effects of Silica-Based CimeXa and Drione Dusts Against Lone Star Tick (Ixodida: Ixodidae) on Cattle

Ixodid ticks vector pathogens of humans, livestock, and wildlife, and occur in tropical and temperate regions worldwide. We used the lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), as a model for other ixodid species, including the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae). We assessed the lethality of CimeXa, an inert silica-based desiccant dust, and Drione, a silica-based desiccant dust with pyrethrin and piperonyl butoxide (PBO), against A. americanum larvae and nymphs on calves. CimeXa was highly lethal to larvae released onto shaved calf skin 72-96 h previously, and moderately toxic to nymphs. It did not affect immature life stages treated after they began feeding because desiccation was offset by ingestion of blood. Being inert, CimeXa can protect cattle from infestation before feeding occurs for a potentially indefinite period of time. Drione killed immatures within 24 h when released on treated skin and when applied to feeding ixodids because of the pyrethrin and PBO (PBO will also reduce resistance to pyrethrin if it develops). When CimeXa was applied to calves with the hair intact, ≈90% and ≈70% of A. americanum larvae and nymphs, respectively, were killed within 24 h and Drione killed 100% of each life stage. Drione also prevented and drastically reduced egg production and hatching. While CimeXa protects against infestation by immatures, Drione will also control ticks that are feeding. When pyrethrin and PBO in Drione eventually degrade, the silica aerogel carrier can continue to protect against infestation indefinitely.

Efficacy of Novaluron + Pyriproxyfen (Tekko Pro) Insect Growth Regulators Against Amblyomma americanum (Acari: Ixodidae), Rhipicephalus (Boophilus) annulatus, Rhipicephalus (Boophilus) microplus, and Rhipicephalus sanguineus

Ixodids are globally distributed pests that transmit many disease agents. Increasing resistance to conventional acaricides raises the need for alternative tactics. Novaluron and pyriproxyfen are insect growth regulators (IGRs) that have variable potencies against acarines. We conducted in vitro and in vivo experiments to assess novaluron + pyriproxyfen (marketed as Tekko Pro) against four ixodid species. Laboratory assays on the brown dog tick, Rhipicephalus sanguineus (Latreille) (Ixodida: Ixodidae), and the lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), reduced metabolic activity in larvae and nymphs. Concentrations of novaluron + pyriproxyfen dried on filter paper impeded molting of larval R. sanguineus (less effective against nymphs). Molting A. americanum larvae were reduced by >95% using 4 and 8 µg/cm2 eliminated molting; nymphal molting was reduced but not halted even at 16 µg/cm2. On calves, novaluron + pyriproxyfen stopped larval A. americanum metabolic function 1 d post-treatment and larvae did not molt. When larvae were released 30 d after treatment, metabolic activity was reduced by 95% and molting was reduced by 94%. Southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae), larvae released 1 d after treatment on calves were 99% prevented from reaching adulthood. The treatment did not interfere with larval development when larvae were released 52 d after treatment. The cattle fever tick, Rhipicephalus (Boophilus) annulatus (Say) (Ixodida: Ixodidae), failed to reach adulthood when larvae were released on calves a day after treatment (residual activity was not assessed for R. annulatus). These IGRs, and possibly others, offer an alternative to conventional acaricides for ixodid control on cattle.

Effects of Laboratory Grade Limonene and a Commercial Limonene-Based Insecticide on Haematobia irritans irritans (Muscidae: Diptera): Deterrence, Mortality, and Reproduction

The horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae), is an important and cosmopolitan blood feeding ectoparasite of cattle. Resistance to conventional insecticides is increasingly problematic and alternative pesticides, including natural products, are being investigated. Limonene is a cyclic monoterpene repellent to some insects that occurs in citrus fruit rinds and in other plants. We assessed laboratory grade limonene and a commercial product, Orange Guard (5.8% AI limonene), against H. irritans irritans in terms of their contact effects upon contact on egg mortality, adults, and larval and pupal development; adult repellency as well as sublethal and fumigation effects. Egg viability declined when they were exposed to Orange Guard at concentrations of 1.45%, 2.9%, and 5.8% whereas laboratory grade limonene at 5.8% and 11.6% was ovicidal. Contact exposure of adult H. irritans irritans to 5.8% laboratory grade limonene and 2.9% Orange Guard caused up to 100 and 88% knockdown (immobilization), respectively. At higher concentrations, laboratory grade limonene and Orange Guard resulted in less, and often shorter periods of knockdown. Although direct contact of 2.9 and 5.8% laboratory grade limonene caused mortality it was negligible when flies were sprayed directly with undiluted Orange Guard. Female H. irritans irritans exposed to sublethal concentrations of Orange Guard did not reduce the numbers of eggs produced, but the undiluted product reduced egg hatchability. Interestingly, limonene and Orange Guard attracted adult H. irritans irritans at concentrations <0.1%. We suggest that the attractancy of unformulated pure limonene might be useful for trapping H. irritans irritans adults.

Lethal and Repellent Effects of the Botanical p-Anisaldehyde on Musca domestica (Diptera: Muscidae)

The house fly, Musca domestica L., is a globally distributed nuisance and disease-carrying urban and livestock pest. Control mostly relies on synthetic insecticides but resistance to them has become problematic. p-Anisaldehyde, a compound found in many edible plants, was assessed for its effects on different life stages of M. domestica. Whereas p-anisaldehyde, applied as an adult contact spray, caused >80% mortality by 30 min at a 30% concentration, egg mortality on treated substrate was complete at 0.1%, and the LC90 was 0.024%. Only 0.5 and 1 ml of 1.5% p-anisaldehyde mixed into 100 g of cow manure curtailed pupation. When the amount of p-anisaldehyde was increased to 2 ml, 0.75% p-anisaldehyde reduced pupation by 95.5%. In static air olfactometer tubes, 0.075% p-anisaldehyde repelled substantial numbers of adult M. domestica within 30 min. Repellency of 60-78% was maintained throughout the 4-h bioassay. This study demonstrates that p-anisaldehyde is strongly bioactive against M. domestica in terms of lethal and nonlethal effects.

Effects of the Botanical Compound p-Anisaldehyde on Horn Fly (Diptera: Muscidae) Repellency, Mortality, and Reproduction

The horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae), is an economically important obligate blood feeder that mainly attacks cattle in Europe, Asia, and North and South America. As horn fly resistance to conventional insecticides becomes more common, alternative control tactics, such as application of bioactive botanical natural products are being investigated. p-Anisaldehyde has been found in many plant species, and it has shown effects that include mortality, attractancy, and interference with host seeking. The series of bioassays we developed was effective for assessing a range of horn fly responses to chemicals and probably those of some other filth fly species. In our study, p-anisaldehyde was lethal to horn fly eggs at concentrations of 0.00001%, and possibly less. Mixed into cow manure, 5000-20,000 ppm p-anisaldehyde reduced horn fly larvae by 85.4%-100%. p-Anisaldehyde caused some immobilization of adult horn flies when exposed by direct contract with spray droplets and by fumigation. Mortality was 90%-100% in response to 5%-10% concentrations by 30 min, and LD50 and LD90 values are reported for five times from 30 min-4 h. Complete horn fly mortality was achieved by fumigation with 0.75% p-anisaldehyde by 3 h in an enclosed space, and we determined that fumigation was more (≈12.5-fold) lethal to adult horn flies than sprayed droplets. Although horn flies were not repelled by p-anisaldehyde in static air tube olfactometers, the compound completely deterred feeding from cotton pads soaked in bovine blood in response to concentrations of 0.6% and greater in ventilated containers. Although horn fly control is not likely to use fumigation methods, p-anisaldehyde might be useful for adult control using sprays and egg and larval control using feed-through techniques. Exposure to sublethal concentrations of p-anisaldehyde did not affect horn fly egg production and hatching. Aside from causing different responses in the same species of arthropod, p-anisaldehyde has a variety of effects on other arthropods. Research on this compound as a potentially multifaceted pest management tool has been sparse. This study, for example, is the first to demonstrate p-anisaldehyde's feeding deterrent and immobilization properties and effects on different life stages.

Botanical Compound p-Anisaldehyde Repels Larval Lone Star Tick (Acari: Ixodidae), and Halts Reproduction by Gravid Adults

The lone star tick, Amblyomma americanum (L.), widely distributed across eastern, southeastern, and midwestern regions of the United States and south into Mexico, is an obligate blood feeder that attaches to three hosts during the larval, nymphal, and adult stages. White-tailed deer and wild turkey are common hosts, as well as a wide variety of other avian and mammalian hosts. Amblyomma americanum is the most frequently reported species of tick to bite humans in the southeastern and southcentral United States, and it can transmit diseases that include erhlichiosis, rickettsiosis, tularemia, and protozoan infections. As A. americanum resistance to conventional insecticides becomes more common, alternative control tactics, such as application of bioactive botanical natural products are being investigated. p-Anisaldehyde has been found in many plant species and it has shown effects that include mortality, attractancy, and interference with host seeking. The series of bioassays we developed was effective for assessing a range of ixodid tick responses to chemicals. This first assessment of p-anisaldehyde on ticks focused mostly on larvae, usually the most vulnerable free-living stage, and on egg production by adults. Contact exposure to larvae resulted in an LD50 of 0.162% and an LD90 of 0.311% p-anisaldehyde. Although fumigation was not lethal to larval A. americanum, p-anisaldehyde was strongly repellent against them in several bioassays that indicate aspects of the repellency such as counteracting the negative geotaxic orientation on a vertical surface, the ability to trap larvae between and inside treatment barriers on different substrates and to divert upward larval movement from one surface to another, and the extent to which larvae fall from a treated surface. The compound at a relatively low concentration applied to gravid adults strongly reduces egg laying and the few eggs that are produced do not hatch. Aside from repelling larval A. americanum and halting reproduction, p-anisaldehyde has a variety of effects on other arthropods including attraction. Research on this compound as a potentially multifaceted pest management tool has been sparse. This study, for example, is the first to demonstrate p-anisaldehyde's repellent properties against an arthropod pest. p-Anisaldehyde might also act as a strong repellent against other tick species.